Systems and methods for safely transporting granular material

ABSTRACT

Systems and methods are provided for safely and efficiently transporting granular material. In one embodiment, a method includes providing an expandable container in an unexpanded state, expanding the expandable container from the unexpanded state to an expanded state, and depositing granular material within the expandable container via an input valve. In this embodiment, the expandable container includes at least a top plate, a bottom plate, an outer material coupled to the top and bottom plates, an input valve associated with the top plate, and a discharge valve associated with the bottom plate. The expandable container can also include a containment bladder, for holding the granular material within the container, and a discharge bladder, for assisting in discharging the granular material from the container.

DESCRIPTION OF THE EMBODIMENTS Field of the Embodiments

The embodiments herein relate generally to systems and methods forsafely transporting granular material, and, more specifically, toimproved systems and methods for safely transporting granularagricultural and industrial materials such as cement, barite, and sandfor use in hydrocarbon fracking operations.

BACKGROUND

Working with certain types of granular material can pose significanthealth risks. According to the U.S. Occupational Safety & HealthAdministration (“OSHA”), inhalation of small crystalline silicaparticles puts workers at risk for silicosis, lung cancer, chronicobstructive pulmonary disease, as well as liver, heart, and kidneydisease. With the increase of hydraulic fracturing (“fracking”) over thepast 5-10 years, the instances of sicknesses and deaths due to silicainhalation have rapidly increased. Many fracking sites fail to meetcurrent OSHA standards. Moreover, OSHA has proposed a new rule loweringthe permissible exposure limit of respirable crystalline silica percubic meter of air. This lower limit will impact almost any industrythat involves transporting or otherwise using silica.

Fracking is a process for stimulating an oil well by fracturingunderground rock using a pressurized liquid. The pressurized liquidconsists primarily of water mixed with a proppant. A typical proppant issand, such as “frac sand,” although other granular materials can be usedas well. The proppant functions to maintain an induced hydraulicfracture open such that the desired oil or gas can be extracted. Asingle fracking well can require several thousand tons of frac sand.

Frac sand is mined and processed in a plant to improve its performancecharacteristics. The sand then gets transported from the plant to thefracking site. This transportation process can involve trains, ships,trucks, conveyors, and other transportation methods. Pneumatic pipesystems and conveyors are routinely used to transport sand from onecontainer to another—for example, from a rail car to a truck or from atruck to a storage facility. Pneumatic and conveyor transfers allowsilica particles to permeate the air in the surrounding area, causing apotential health hazard to any workers nearby.

In addition to the health hazards, the typical processes fortransporting frac sand have additional drawbacks. For example, acontainer (e.g., a rail car or a truck) designed to hold frac sand maynot be useful for carrying other items. That is, once the load of fracsand has been deposited, the rail car or container cannot be used foranother purpose; instead, it must be returned to a location where it canbe refilled with frac sand. The lack of reusability increasestransportation costs and, as a result, the overall cost of fracking.

Therefore, a need exists for systems and methods for safely andefficiently transporting granular material. More specifically, a needexists for systems and methods for transporting granular material in amanner that limits respirable silica emissions, eliminates harmfulpneumatic transfers, and provides lower transport costs.

SUMMARY

Embodiments described herein include systems and methods for safely andefficiently transporting granular material. In one embodiment, a methodincludes providing an expandable container in an unexpanded state,expanding the expandable container from the unexpanded state to anexpanded state, and depositing granular material within the expandablecontainer via an input valve. In this embodiment, the expandablecontainer includes at least a top plate, a bottom plate, an outermaterial coupled to the top and bottom plates, an input valve associatedwith the top plate, and a discharge valve associated with the bottomplate. The expandable container can also include a containment bladderfor holding of the granular material within the container and protectingit from the elements, and a discharge bladder for assisting indischarging the granular material from the container.

In another embodiment, the method also includes transporting theexpandable container. The method can further include discharginggranular material from the expanded container via the discharge valve.The discharge bladder may be inflated in a manner that urges or biasesthe granular material within the containment bladder toward thedischarge valve. Discharging the granular material may cause theexpandable container to return to its unexpanded state. Once in itsunexpanded state, the expandable container may be stacked on top of asimilar expandable container, also in an unexpanded state, fortransporting. This can, for example, require half or fewer train cars toreturn the expandable containers than is needed for transporting thefull containers.

In one embodiment, the expandable container includes a restraint deviceremovably coupled to the top and bottom plates and/or support membersassociated with the top and bottom plates. Expanding the expandablecontainer may include the step of removing the restraint device.

In yet another embodiment, an expandable container is provided forsafely transporting granular material. The expandable container caninclude a top plate, a bottom plate, an outer material coupled to thetop and bottom plates, an input valve associated with the top plate, anda discharge valve associated with the bottom plate. Furthermore, theexpandable container can be expanded by applying opposing forces to thetop and bottom plates, respectively.

The expandable container may include a containment bladder coupled tothe top and bottom plates. The outer material may include at least oneKevlar or Kevlar-reinforced band, and/or may be coupled to the top andbottom plates via retaining rings. The input valve and/or dischargevalve may include a spring-loaded plate. A discharge bladder may beincluded, and can be positioned outside the containment bladder andinside the outer material. The discharge bladder can be configured to beinflated via an inflation port. Once inflated, the discharge bladder canprovide a shape that biases the granular material within the containmentbladder toward the discharge valve.

The expandable container can also include a restraint device that can beremovably coupled to the top and bottom plates, thereby limiting thevertical expansion of the container. The top and/or bottom plates of theexpandable container can also include reinforcement members. Thesereinforcement members can be coupled to the input and/or dischargevalves, respectively.

Both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not intended torestrict the scope of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this disclosure, illustrate various embodiments and aspects ofthe present invention. In the drawings:

FIG. 1 is an illustration of an example embodiment of an expandablecontainer for transporting granular material;

FIG. 2 is a cross-sectional view of an example embodiment of an inputvalve of an expandable container;

FIG. 3 is a cross-sectional view of an example embodiment of anexpandable container having a discharge valve and discharge bladder;

FIG. 4A is an illustration of an example embodiment of an expandablecontainer in an unexpanded state;

FIG. 4B is an illustration of an example embodiment of an expandablecontainer in an expanded state; and

FIG. 5 is a flow chart of an example method of transporting granularmaterial using an expandable container.

DETAILED DESCRIPTION

Reference will now be made in detail to the present exemplaryembodiments, including examples illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The expandable containers described herein may be used to store andtransport granular material, such as frac sand. In one exampleembodiment, the expandable container may have a containment volume ofabout 500 cubic feet. In that example the expandable container may beabout 10 feet tall in its expanded state and have a diameter of about 8feet. The height and diameter, and therefore the containment volume, ofthe container may be varied according to the particular transportationneeds of a project. For example, the container may have an expandedheight of between 6-14 feet, and may have a diameter of between 4-12feet. Other sized may be used as well, and these examples are notintended to limit this disclosure in any way.

FIG. 1 is an illustration of an example embodiment of an expandablecontainer 100 for transporting granular material. The expandablecontainer includes a top plate 110 and bottom plate 120, with an outermaterial 130 coupled to the top and bottom plates 110, 120. The top andbottom plates 110, 120 may be constructed from a rigid material, such assteel or other metals and alloys. The outer material 130 can be coupledto the top and bottom plates 110, 120 via locking rings 150. Lockingrings 150 secure the outer material 130 to the top and bottom plates110, 120 by applying a clamping force. Locking rings 150 may fit flushwith the side of the top and/or bottom plates 110, 120, or may fit atleast partially inside a slot provided in the top and/or bottom plates110, 120. Locking rings 150 may be tightened by mechanical means to atension sufficient to retain the outer material 130 during use.

The outer material 130 can be constructed from a robust yet flexiblematerial such as, for example, Kevlar or other material having similarlyhigh elastic modulus and/or tensile strength measurements. For example,the outer material 130 can be made from a fabric having an elasticmodulus of between about 100 and 200 GPa. In some examples, the outermaterial 130 can be made from a material having a tensile strength ofbetween about 2000 and 4000 MPa. In other examples, material havingcharacteristics outside of these ranges can be used. However, a materialwith these characteristics can prevent bulging and thereby maintain theuniform cross-sectional diameter of the container as the outer material.The outer material 130 functions to contain the contents of theexpandable container 100, including any internal bladders or containmentvessels. The outer fabric material 130 can be stronger than steel, on aper-weight basis. However, it also provides flexibility such that theexpandable container 100 can be expanded or contracted in an efficientand reliable manner. At the same time, however, the outer material 130is strong enough to resist tearing or rupturing during use, which mayinvolve heavy machinery and large forces or loads.

For increased strength and overall robustness of the container, supportmembers 160 may be coupled to the top plate 110 and/or bottom plate 120.The support members 160 provide increased rigidity of the top and bottomplates 110, 120, and enable multiple expandable containers 100 to bestacked on top of one another. The support members 160 also provide amechanism to manipulate the expandable container 100 itself. Forexample, the loading process may require the top plate 110 to be liftedand/or vibrated to efficiently fill the containment volume with granularmaterial. In this scenario the top plate 110 can be gripped via supportmembers 160 and manipulated as needed. The container 100 can be filledwith sand while lifted, allowing the weight of the sand to expand thecontainer 100 downward. Then the full container 100 can 100 can beplaced on a train car or other transport.

Additionally, support members 160 can be used to temporarily fix theheight of the expandable container 100. As discussed further withrespect to FIG. 4A, the support members 160 can be connected via anadditional member that limits the expansion or contraction abilities ofthe expandable container 100 while connected. Finally, the supportmembers 160 may also be coupled to the input valve 140 and/or dischargevalve, as discussed in more detail below.

With respect to FIG. 1, a discharge bladder valve 170 is also shown. Thedischarge bladder valve 170 can be used to provide fluid, such ascompressed air, to one or more discharge bladders inside the expandablecontainer 100. This functionality is discussed in more detail below withrespect to FIG. 3.

FIG. 2 is a cross-sectional view of an example embodiment of input valve140. The same architecture and components may be used for a dischargevalve as well—therefore, any reference herein with respect to an “input”valve, or its components, may be applied in similar fashion to adischarge valve. FIG. 2 shows a support member 160 coupled to both thetop plate 110 and the input valve 140. The support member 160 may becoupled to the top plate 110 via fasteners or welds along the length, ora portion of the length, of the support member 160. The support member160 may be coupled to the input valve 140 via valve shaft 220. Valveshaft 220 can be provided as a solid or hollow bar of metal or otherhigh-strength material in order to provide a solid base upon which theinput valve 140 functions. The support member 160 can be coupled tovalve shaft 220 by welding, fastening, or other mechanical connectiontechniques.

A valve plate 210 can be used to control the flow of material into orout of a valve. The valve plate 210 can be provided as a circular diskwith a hole that accommodates valve shaft 220, such that the valve plate210 can slidably move along the valve shaft 220. A biasing mechanism,such as a spring 240, can be used along at least a portion of the valveshaft 220. Spring 240 biases the valve plate 210 in a manner that willcause the valve plate 210 to sit flush with the top plate 110 in itsresting position (i.e., when no external forces are being applied to thevalve plate 210). A valve pin 230 can be provided along the valve shaft220 to abut one end of the spring 240, while the other end of the spring240 abuts the valve plate 210.

To operate the input valve 140, the valve plate 210 is depressed suchthat it moves along the valve shaft 220 toward the valve pin 230,compressing the spring 240. In practice, the valve plate 210 can bedepressed by a loading apparatus. For example, the nozzle of a hopper,tube, or pipe carrying granular material can be shaped to contact anddepress the valve plate 210. In some embodiments one mechanism is usedto depress the valve plate 210 while a separate component provides thegranular material. Any device that depresses the valve plate 210 towardthe valve pin 230 can be used to open the input valve 140.

As mentioned above, a discharge valve may incorporate the same, orsimilar, components described in FIG. 2 with respect to the input valve140. FIG. 3 shows a cross-sectional view of an example embodiment of anexpandable container having a discharge valve 320 and discharge bladder340. Similar to the input valve 140 described with respect to FIG. 2,the discharge valve 320 of FIG. 3 includes a valve shaft 322, valveplate 324, valve pin 328, and a spring 326. The discharge valve 320 isoperated by depressing or otherwise moving the valve plate 324 along thevalve shaft 322 toward the valve pin 328, compressing the spring 326 andexposing an opening in the bottom plate 310. The discharge valve 320 ofFIG. 3 is shown in an open position, where the granular material 350 mayfreely flow out.

FIG. 3 also shows a containment bladder 330 having an amount of granularmaterial 350. The containment bladder 330 is located within the outermaterial 130 and may be constructed from a gas-impermeable membrane,such as nylon. Other materials may be used as well. Suitable materialsinclude any material that is sufficiently pliable and strong, and doesnot allow any granular material, dust, or gases to escape through thematerial. The containment bladder 330 can be coupled to the outermaterial 130, support members 160, or the top and/or bottom plates 110,310. In the embodiment depicted in FIG. 3, the containment bladder 330is coupled to at least the bottom plate 310.

FIG. 3 also shows discharge bladder 340. Discharge bladder 340 is shownin two portions in FIG. 3—each portion roughly triangular in crosssection. These two portions represent a cross-sectional view of a singledischarge bladder 340 that wraps around the expandable container 100. Inthis embodiment the discharge bladder 340 is one bladder; however, inother embodiments the discharge bladder 340 may include multiplebladders working in combination with one another. In either case, thebladders may be inflated with a fluid, such as air or another gas, viadischarge bladder valve 170.

Discharge bladder 340 can be inflated during the discharge process whenthe granular material 350 begins to run low. One purpose of thedischarge bladder 340 is to prevent granular material 350 from remainingtrapped inside the containment bladder 330 due to the flat-bottomedshape of the expandable container 100. Discharge bladder 340 fills inthe areas that may trap the granular material 350, thereby urging theremaining granular material 350 to exit the discharge valve 320.

Discharge bladder 340 may inflate automatically, for example by usinginput from a sensor that determines the amount of granular material 350remaining in the expandable container 100. In this embodiment dischargebladder 340 may be connected to a built-in pump provided within, orattached to, the expandable container 100. In other embodiments thedischarge bladder 340 can be inflated manually by attaching an air hoseto the discharge bladder valve 170.

FIGS. 4A and 4B each show an expandable container 100 similar to thecontainer of FIG. 1. The expandable container 100 in FIG. 4A is shown ina collapsed or unexpanded state, whereas the expandable container 100 inFIG. 4B is shown in an expanded state. FIGS. 4A and 4B also show arestraint device 410 that can be coupled to at least one support member160. Although only a single restraint device 410 is shown, multiple maybe used. When the restraint device 410 is secured to two support members160 associated with the top and bottom plates 110, 120, respectively (asshown in FIG. 4A), the expandable container 110 is prevented fromexpanding.

The unexpanded state of FIG. 4A can be useful for transporting emptycontainers 100 in an efficient manner. For example, thirty trucks may besent to a worksite, with each truck carrying two expandable containers100 filled with granular material. After depositing the granularmaterial at the worksite, the expandable containers 100 can be securedin their unexpanded states via restraint device 410 and stacked threecontainers high, such that all sixty containers can be loaded onto tentrucks. This lowers the transportation cost associated with transportinggranular material.

To prepare the expandable container 100 of FIG. 4A for loading, therestraint device 410 can be decoupled from one of the support members160. As shown in FIG. 4B, for example, the restraint device 410 can bedecoupled from a support member 160 associated with the bottom plate. Inorder to secure the restraint device 410 when it is only attached to onesupport member 160, a restraint strap may be provided along the side ofthe expandable container 100. For example, the restraint strap may beattached to the outer material 130.

FIG. 5 provides a flow chart of an example method of transportinggranular material using the expandable containers described herein. Atstep 510, an expandable container is provided. In the embodiment of FIG.5, the container is provided in an unexpanded state; however, thecontainer may be provided in either an expanded or unexpanded state atthis step.

If a restraint device is installed such that the container is preventedfrom expanding, the restraint device is removed at step 520.

At step 530, the expandable container is expanded. This may involve, forexample, lifting the expandable container using the top plate, orsupport members attached to the top plate, and allowing the container toexpand via the weight of the bottom plate. This step may also involvesome amount of vibration or movement to encourage the container toexpand sufficiently.

At step 540, granular material is deposited into the expandablecontainer via an input valve. This step may occur simultaneously withstep 530, or may occur after step 530. For example, when the expandablecontainer is lifted from the top plate, pouring sand into the liftedcontainer can provide enough weight to cause the bottom of the containerto expand downward. Step 540 includes accessing the input valve bydepressing the valve plate, as described with respect to FIG. 2. Thisstep also includes supplying granular material to the expandablecontainer, for example by using a hopper, conduit, hose, funnel, orother device that directs the granular material into the input valve.The device supplying the granular material may also depress the valveplate, or these actions may be done separately by two different devices.

Step 540 may also include vibrating or otherwise applying force to theexpandable container as the granular material is deposited. Theapplication of force spreads the granular material within the expandablecontainer and allows for an uninterrupted flow of material into thecontainer.

At step 550, the filled expandable container is transported to itsdestination. Because a filled container can be quite heavy, machinerymay be used to lift the filled container and place it on a truck, ship,train car, or other transportation device. In some embodiments, the samemachinery is used to expand the container at step 530 and load thecontainer at step 550. In other embodiments separate machines are usedat each step.

At step 560, the granular material is discharged from the expandablecontainer at its desired location. Depending on the type of transportvehicle used, the filled containers may need to be removed from thetransport vehicle before the granular material is discharged. Todischarge the material, the container is positioned in the desiredlocation and the valve plate of the discharge valve is depressed, asshown in FIG. 3. This opens the valve and allows material to flow fromthe container.

Step 570 includes inflating the discharge bladder (or bladders, if thecontainer is equipped with more than one) such that any remaininggranular material is expelled through the discharge valve. As describedwith respect to FIG. 3, the discharge bladder may inflate automaticallybased on a perceived level of material in the container, or may beinflated manually by, for example, attaching a source of compressed airto the discharge bladder valve.

At step 580, the now-empty expandable container is provided in anunexpanded state due to its lack of contents. At this step the restraintdevice may be installed, or reinstalled, such that it connects to atleast one support member along the top plate and one support memberalong the bottom plate. Once secured, the restraint device maintains theunexpanded geometry of the container. This allows for multipleunexpanded containers to be stacked on top of one another—for example,on a truck or other shipping vehicle. Once the unexpanded containers arereturned to the storage location for the granular material, they may befilled again starting with Step 510.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

What is claimed is:
 1. A method of safely transporting granularmaterial, comprising: providing an expandable container in an unexpandedstate, the expandable container comprising: a top plate; a bottom plate;an outer material; an input valve associated with the top plate; and adischarge valve associated with the bottom plate, expanding theexpandable container from the unexpanded state to an expanded state bylifting the expandable container at the top plate; and depositinggranular material within the expandable container via the input valve.2. The method of claim 1, wherein depositing the granular materialcauses the expandable container to expand while in a lifted state. 3.The method of claim 1, further comprising discharging granular materialfrom the expanded container via the discharge valve.
 4. The method ofclaim 3, wherein said discharging causes the expandable container toreturn to the unexpanded state.
 5. The method of claim 4, furthercomprising stacking the expandable container, in the unexpanded state,on top of another expandable container in an unexpanded state.
 6. Themethod of claim 1, wherein the expandable container comprises arestraint device removably coupled to the top and bottom plates and/orsupport members associated with the top and bottom plates, and whereinexpanding the expandable container further comprises removing therestraint device.
 7. The method of claim 1, wherein the expandablecontainer comprises a containment bladder coupled to the top and bottomplates.
 8. The method of claim 3, wherein discharging further comprisesinflating a discharge bladder.
 9. The method of claim 8, where inflatingthe discharge bladder biases the granular material within thecontainment bladder toward the discharge valve.
 10. An expandablecontainer for safely transporting granular material, comprising: a topplate; a bottom plate; an outer material coupled to the top and bottomplates; an input valve associated with the top plate; and a dischargevalve associated with the bottom plate, wherein the expandable containercan be expanded by applying opposing forces to the top and bottomplates, respectively.
 11. The expandable container of claim 10, furthercomprising a containment bladder coupled to the top and bottom plates.12. The expandable container of claim 10, wherein the outer materialcomprises a fabric having at least one of: an elastic modulus of betweenabout 100 and 200 GPa, or a tensile strength of between about 2000-4000MPa.
 13. The expandable container of claim 10, wherein the outermaterial is coupled to the top and bottom plates via retaining rings.14. The expandable container of claim 10, wherein the input valve and/ordischarge valve comprises a spring-loaded plate.
 15. The expandablecontainer of claim 10, further comprising a discharge bladder positionedoutside the containment bladder.
 16. The expandable container of claim15, wherein the discharge bladder is configured to be inflated via aninflation port.
 17. The expandable container of claim 16, wherein thedischarge bladder, once inflated, provides a shape that biases thegranular material within the containment bladder toward the dischargevalve.
 18. The expandable container of claim 10, further comprising arestraint device configured to be removably coupled to the top andbottom plates, thereby preventing the expandable container fromexpanding and/or contracting.
 19. The expandable container of claim 10,wherein the top and/or bottom plate further comprises reinforcementmembers.
 20. The expandable container of claim 19, wherein thereinforcement members of the top and/or bottom plate are coupled to theinput and/or discharge valves, respectively.